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IP Session 19 INST 346 Technologies, Infrastructure and - PowerPoint PPT Presentation

May 09, 2023 •273 likes •577 views

IP Session 19 INST 346 Technologies, Infrastructure and Architecture Goals for Today IPv4 DHCP IPv6 NAT Network layer application transport segment from transport network sending to receiving host data link

  1. IP Session 19 INST 346 Technologies, Infrastructure and Architecture

  2. Goals for Today • IPv4 • DHCP • IPv6 • NAT

  3. Network layer application  transport segment from transport network sending to receiving host data link physical network network  on sending side data link data link network physical physical data link encapsulates segments physical network network data link data link into datagrams physical physical  on receiving side, delivers network network data link data link segments to transport physical physical network data link layer physical application network transport  network layer protocols data link network network physical data link network data link in every host, router physical data link physical physical  router examines header fields in all IP datagrams passing through it

  4. IP datagram format IP protocol version 32 bits total datagram number length (bytes) header length type of head. ver length (bytes) service len for “ type ” of data fragment fragmentation/ 16-bit identifier flgs offset reassembly max number upper time to header remaining hops live layer checksum (decremented at 32 bit source IP address each router) 32 bit destination IP address upper layer protocol to deliver payload to e.g. timestamp, options (if any) record route data taken, specify how much overhead? (variable length, list of routers  20 bytes of TCP typically a TCP to visit.  20 bytes of IP or UDP segment)  = 40 bytes + app layer overhead

  5. IP addressing: introduction 223.1.1.1  IP address: 32-bit identifier for host, router 223.1.2.1 interface 223.1.1.2 223.1.1.4 223.1.2.9  interface: connection between host/router and 223.1.3.27 physical link 223.1.1.3 223.1.2.2 • router ’ s typically have multiple interfaces • host typically has one or two interfaces (e.g., wired 223.1.3.1 223.1.3.2 Ethernet, wireless 802.11)  IP addresses associated with each interface 223.1.1.1 = 11011111 00000001 00000001 00000001 223 1 1 1

  6. Subnets  IP address: 223.1.1.1 • subnet part - high order bits 223.1.2.1 223.1.1.2 223.1.1.4 223.1.2.9 • host part - low order bits 223.1.2.2  what ’ s a subnet ? 223.1.3.27 223.1.1.3 • device interfaces with subnet same subnet part of IP address 223.1.3.2 223.1.3.1 • can physically reach each other without intervening router network consisting of 3 subnets

  7. IP addressing: CIDR CIDR: Classless InterDomain Routing • subnet portion of address of arbitrary length • address format: a.b.c.d/x, where x is # bits in subnet portion of address host subnet part part 11001000 00010111 00010000 00000000 200.23.16.0/23

  8. IP addresses: how to get one? Q: how does network get subnet part of IP addr? A: gets allocated portion of its provider ISP ’ s address space ISP's block 11001000 00010111 00010000 00000000 200.23.16.0/20 Organization 0 11001000 00010111 00010000 00000000 200.23.16.0/23 Organization 1 11001000 00010111 00010010 00000000 200.23.18.0/23 Organization 2 11001000 00010111 00010100 00000000 200.23.20.0/23 ... ….. …. …. Organization 7 11001000 00010111 00011110 00000000 200.23.30.0/23

  9. IP addressing: the last word... Q: how does an ISP get block of addresses? A: ICANN: Internet Corporation for Assigned Names and Numbers http://www.icann.org/ • allocates addresses • manages DNS • assigns domain names, resolves disputes

  10. Hierarchical addressing: route aggregation hierarchical addressing allows efficient advertisement of routing information: Organization 0 200.23.16.0/23 Organization 1 “ Send me anything 200.23.18.0/23 with addresses beginning Organization 2 . 200.23.16.0/20 ” 200.23.20.0/23 Fly-By-Night-ISP . . . Internet . . Organization 7 200.23.30.0/23 “ Send me anything ISPs-R-Us with addresses beginning 199.31.0.0/16 ”

  11. DHCP: Dynamic Host Configuration Protocol goal: allow host to dynamically obtain its IP address from network server when it joins network • can renew its lease on address in use • allows reuse of addresses (only hold address while connected/ “ on ” ) • support for mobile users who want to join network (more shortly) DHCP overview: • host broadcasts “ DHCP discover ” msg [optional] • DHCP server responds with “ DHCP offer ” msg [optional] • host requests IP address: “ DHCP request ” msg • DHCP server sends address: “ DHCP ack ” msg

  12. DHCP client-server scenario DHCP 223.1.1.0/24 server 223.1.2.1 223.1.1.1 223.1.1.2 arriving DHCP 223.1.1.4 223.1.2.9 client needs address in this network 223.1.2.2 223.1.3.27 223.1.1.3 223.1.2.0/24 223.1.3.2 223.1.3.1 223.1.3.0/24

  13. DHCP client-server scenario DHCP server: 223.1.2.5 arriving DHCP discover client src : 0.0.0.0, 68 Broadcast: is there a dest.: 255.255.255.255,67 DHCP server out there? yiaddr: 0.0.0.0 transaction ID: 654 DHCP offer src: 223.1.2.5, 67 Broadcast: I’m a DHCP dest: 255.255.255.255, 68 server! Here’s an IP yiaddrr: 223.1.2.4 transaction ID: 654 address you can use lifetime: 3600 secs DHCP request src: 0.0.0.0, 68 dest:: 255.255.255.255, 67 Broadcast: OK. I’ll take yiaddrr: 223.1.2.4 that IP address! transaction ID: 655 lifetime: 3600 secs DHCP ACK src: 223.1.2.5, 67 dest: 255.255.255.255, 68 Broadcast: OK. You’ve yiaddrr: 223.1.2.4 got that IP address! transaction ID: 655 lifetime: 3600 secs

  14. DHCP: more than IP addresses DHCP can return more than just allocated IP address on subnet: • address of first-hop router for client • name and IP address of DNS sever • network mask (indicating network versus host portion of address)

  15. DHCP: example  connecting laptop needs DHCP DHCP its IP address, addr of UDP DHCP IP first-hop router, addr of DHCP Eth DHCP DNS server: use DHCP Phy  DHCP request encapsulated DHCP in UDP, encapsulated in IP, encapsulated in 802.1 DHCP 168.1.1.1 DHCP DHCP Ethernet UDP DHCP IP DHCP  Ethernet frame broadcast Eth router with DHCP DHCP (dest: FFFFFFFFFFFF ) on LAN, Phy server built into received at router running router DHCP server  Ethernet demuxed to IP demuxed, UDP demuxed to DHCP

  16. DHCP: example  DCP server formulates DHCP DHCP DHCP ACK containing UDP DHCP client ’ s IP address, IP IP DHCP address of first-hop Eth DHCP router for client, name & Phy IP address of DNS server  encapsulation of DHCP server, frame forwarded DHCP DHCP to client, demuxing up to UDP DHCP DHCP at client IP DHCP Eth router with DHCP DHCP  client now knows its IP Phy server built into DHCP address, name and IP router address of DSN server, IP address of its first-hop router

  17. DHCP: Wireshark Message type: Boot Reply (2) reply output (home LAN) Hardware type: Ethernet Hardware address length: 6 Hops: 0 Transaction ID: 0x6b3a11b7 Seconds elapsed: 0 Bootp flags: 0x0000 (Unicast) Message type: Boot Request (1) Client IP address: 192.168.1.101 (192.168.1.101) Hardware type: Ethernet Your (client) IP address: 0.0.0.0 (0.0.0.0) Hardware address length: 6 request Next server IP address: 192.168.1.1 (192.168.1.1) Hops: 0 Relay agent IP address: 0.0.0.0 (0.0.0.0) Transaction ID: 0x6b3a11b7 Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a) Seconds elapsed: 0 Server host name not given Bootp flags: 0x0000 (Unicast) Boot file name not given Client IP address: 0.0.0.0 (0.0.0.0) Magic cookie: (OK) Your (client) IP address: 0.0.0.0 (0.0.0.0) Option: (t=53,l=1) DHCP Message Type = DHCP ACK Next server IP address: 0.0.0.0 (0.0.0.0) Option: (t=54,l=4) Server Identifier = 192.168.1.1 Relay agent IP address: 0.0.0.0 (0.0.0.0) Option: (t=1,l=4) Subnet Mask = 255.255.255.0 Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a) Option: (t=3,l=4) Router = 192.168.1.1 Server host name not given Option: (6) Domain Name Server Boot file name not given Length: 12; Value: 445747E2445749F244574092; Magic cookie: (OK) IP Address: 68.87.71.226; Option: (t=53,l=1) DHCP Message Type = DHCP Request IP Address: 68.87.73.242; Option: (61) Client identifier IP Address: 68.87.64.146 Length: 7; Value: 010016D323688A; Option: (t=15,l=20) Domain Name = "hsd1.ma.comcast.net." Hardware type: Ethernet Client MAC address: Wistron_23:68:8a (00:16:d3:23:68:8a) Option: (t=50,l=4) Requested IP Address = 192.168.1.101 Option: (t=12,l=5) Host Name = "nomad" Option: (55) Parameter Request List Length: 11; Value: 010F03062C2E2F1F21F92B 1 = Subnet Mask; 15 = Domain Name 3 = Router; 6 = Domain Name Server 44 = NetBIOS over TCP/IP Name Server ……

  18. IPv6: motivation  initial motivation: 32-bit address space soon to be completely allocated.  additional motivation: • header format helps speed processing/forwarding • header changes to facilitate QoS IPv6 datagram format: • fixed-length 40 byte header

  19. IPv6 datagram format priority: identify priority among datagrams in flow flow Label: identify datagrams in same “ flow. ” (concept of “ flow ” not well defined). next header: identify upper layer protocol for data ver pri flow label payload len hop limit next hdr source address (128 bits) destination address (128 bits) data 32 bits

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